*The following is excerpted from an online article from HealthDay.
Teenagers who smoke marijuana daily may have lingering memory problems and structural abnormalities in the brain, even after they stop using the drug, a small study suggests.
Researchers found that young adults who'd smoked pot heavily as teens performed worse on memory tests than their peers who'd never used the drug regularly. And on brain scans, they tended to show differences in the shape of the hippocampus -- a brain structure involved in forming long-term memories.
However, the findings, reported March 12 in the journal Hippocampus, do not prove that marijuana is the culprit.
That's partly because the study participants were assessed only once, which leaves the chicken-and-egg question open, said lead researcher Matthew Smith.
"We can't know that it's causing the memory impairment," said Smith, an assistant professor of psychiatry and behavioral sciences at Northwestern University Feinberg School of Medicine, in Chicago.
However, he pointed out that other research has found a link between teenagers' heavy marijuana use and lingering memory problems, as well as a loss in IQ points. Similarly, brain-imaging studies have found that habitual pot smokers show differences in the volume and shape of the hippocampus, versus non-users.
What's more, the young adults in this study had been marijuana-free for an average of two years. That suggests that if heavy use alters teenagers' brain structure, or dims their memories, the effects do not quickly go away, Smith said.
More research is needed, he said, to see just how long those effects might last after young people stop smoking pot.